JPH048409Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to aperture blades for controlling the amount of light used in optical devices, and particularly to the blade profile shape of a two-blade diaphragm.

[Conventional technology]

This type of diaphragm device used in optical devices uses a so-called iris diaphragm, which is composed of many blades, for high-end models, and the aperture can be adjusted at any aperture value. It is designed to have a shape that approximates a circular shape.

On the other hand, low-priced apertures have a small number of blades, and for example, the smallest two-blade diaphragm is in practical use. There are various blade contour shapes for a two-blade diaphragm, but for example, the facing blades 1 and 2 are in the shape of a tadpole's tail as shown in Fig. 3, and square blades are shown in Fig. 4 11 and 12. A combination of opposing blades at one right angle is generally known. 3 indicates the overlapping portion of both blades.

However, in the former example (Figure 3),
Problems include so-called "different centers" where the geometric center of gravity of the aperture changes depending on the aperture value, differences in "blur" depending on direction due to changes in aspect ratio, and ghost shapes caused by point light sources. . On the other hand, in the latter example (Figure 4), the geometric center of gravity of the aperture does not change depending on the aperture value, and the length and width are constant, but the sides that make up the aperture can only be in two directions. Therefore, the image is distorted only in the above two directions during defocusing, and the ghost shape of the point light source is square, which is likely to be psychologically disliked.

As a means of solving these problems, as shown in FIG. 5, two aperture blades have a contour shape that is a combination of a plurality of circular arcs 23 and 24, each having its center on a line in the direction of movement of the blades passing through the optical axis of the optical system. 21, 22
A proposal for a diaphragm having a
(see issue).

According to this proposed example, at multiple aperture values,
Openings each having an approximate circular shape can be obtained, and the above-mentioned conventional drawbacks can be overcome to some extent.

[Problem that the invention attempts to solve]

However, when using the aperture blade contour shape of the proposed example as described above, the aperture shape of each aperture value where both aperture blades move oppositely in the horizontal direction is the fifth
It will look like figures a, b, c, d, and e. a is the maximum aperture, e is the aperture at the minimum aperture, b, c, and d are the aperture shapes at intermediate aperture values, among which,
d indicates the aperture at approximately the normal aperture. As is clear from the figure, an aperture shape that is circular or approximately circular can be obtained in three aperture value states: maximum aperture a, aperture d at the regular aperture, and aperture e at the minimum aperture. Since the aspect ratio is different in the aperture d at the time, there is a drawback that a "difference in blur" occurs depending on the direction due to this.

The present invention was made in view of the problems of the conventional proposals as described above, and eliminates the above-mentioned drawbacks.
The object of the present invention is to provide a two-blade diaphragm blade profile shape that can obtain an aperture shape that approximates a circle at a plurality of aperture values and has an aspect ratio that is approximately 1.

[Means for solving problems]

Therefore, in the present invention, the aperture contour shape of the two blades is configured such that the two aperture blades move oppositely along the movement line passing through the optical axis of the optical system, and The aperture device has a contour shape of each of the aperture blades formed by combining substantially circular arcs, wherein the plurality of circular arcs are orthogonal to a first group of circular arcs having a center of curvature on the line of movement and the line of movement. a second circular arc group having its center of curvature on the line, the first circular arc group and the second circular arc group being located approximately equidistant from each other from a predetermined point on the movement line;
The above objective is achieved by forming each of the circular arcs to have approximately the same size.

[Effect]

Due to the two-blade opening contour shape as described above,
The aperture shape at each aperture value approximates a circle, and its aspect ratio approaches 1.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. FIG. 1 shows a diagram corresponding to FIG. 5 of the conventionally proposed example of an embodiment of the two-blade contour shape according to the present invention, and FIG. A diagram corresponding to FIG. 6 of the opening shape is shown.

As mentioned above, when using the aperture blades shown in the previously proposed example shown in Fig. 5, the difference in the aspect ratio of the aperture shape (Fig. 6 d) during normal aperture is due to the movement of the optical axis through the blades. Multiple arcs 23, 24 only on line X
This is due to the combination of . Therefore,
In order to make the aspect ratio of figure d approach 1, straight line
It is sufficient to have an arc in the direction perpendicular to the direction. Therefore, in this embodiment (FIG. 1), a circular arc 23' having the minimum radius is added to the aperture blades 21 and 22 shown in FIG. 3 in the direction Y orthogonal to the straight line X direction. Therefore, the aperture shapes b, c, and d in Figure 6 at intermediate aperture values are as shown in Figure 2 b, c, and d, respectively, and the aperture shape at the regular aperture in Figure 2 is circular as shown in d. The directions are similar, and the aspect ratio approaches 1, making it possible to achieve the desired purpose.

In this embodiment, the arc 23' added in the direction perpendicular to the straight line X has the same radius as the arc 23 with the smallest radius. Of course, it is not limited to only circular arcs.

Furthermore, in the embodiment described above, the opening is changed by sliding the two blades in the horizontal direction, but as shown in FIG. It is also known as a publicly known technique that the aperture is changed by rotating around a rotation locus 72 that includes the optical axis, and the present invention can be applied in exactly the same manner to obtain the same effect with this type of aperture. be able to.

[Effect of idea]

As explained above, according to the present invention, 2
By appropriately selecting the aperture contour shape of the aperture blades, even in a simple and low-cost two-blade diaphragm device, a circular shape can be approximated at multiple aperture values, and one
It has become possible to obtain aperture shapes with aspect ratios close to .

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the two-blade contour shape according to the present invention, FIGS. 2
Two examples of blade shapes, FIGS. 5 and 6, correspond to FIGS. 1 and 2 of the conventionally proposed example, respectively, and FIG. 7 shows a blade shape of another embodiment of the present invention. 31, 32...Aperture blade, 23, 23', 24
...Circular arc (arc), X...Blade movement line, Y...X orthogonal line.

Claims (1)

[Claims for Utility Model Registration] Two aperture blades are configured to move oppositely along a movement line passing through the optical axis of the optical system, and each of the aperture blades is constructed by combining a plurality of substantially circular arcs. The aperture device is formed with a contour shape, wherein the plurality of circular arcs include a first group of circular arcs having a center of curvature on the line of movement, and a second group of circular arcs having a center of curvature on a line orthogonal to the line of movement. a group of circular arcs, the first group of circular arcs and the second group of circular arcs are located approximately equidistant from each other from a predetermined point on the movement line,
A two-blade diaphragm device characterized in that each blade has substantially circular arcs having substantially the same size.